1. Field of the Invention
The present invention relates to an image processing apparatus which employs a spatial light modulator and a laser beam scanning system for processing an image data.
2. Description of the Related Art
Inventors know a color copying machine for creating, editing, and copying a color image. In general, such the color copying machine employs an analog type or a digital type, each of which has the corresponding merits and demerits.
As for color correction or tone processing, an analog type color copying machine is inferior to a digital type color copying machine. This is because the analog type color copying machine is arranged to directly expose and develop an optical image for creating a color copy, on the contrary, the digital type color copying machine is arranged to convert an original image data into a digital signal with an image scanner and output the color copy from a printer depending on the converted digital signal.
As for the resulting color copy, the analog type color copying machine can provide a smoother image (resolution is about 800 DPI) but inferior color reproduction, because the analog type machine cannot easily perform color masking (for separating black from chromatic colors) of an image data. In actual, the black lines are colored into chromatic colors on the resulting copy. The digital type color copying machine, on the other hand, provides easier color masking and superior color reproduction. However, the digital type machine has some difficulty in making the resulting copy more fine. That is, as more reading pixels are prepared for creating more fine copy, more memories are necessary. For the purpose, the digital type machine requires a high-speed processor and a large capacity memory, resulting in pushing up the cost of the digital type machine far higher than the analog type machine.
As will be appreciated from the above description, the analog type color copying machine is superior in treating a large amount of copies, while the digital type color copying machine is superior in creating a graphic design copy to be color-reproduced as exactly as possible or printing a small amount of copies.
The analog type color copying machine and the digital type color copying machine have been selected on the basis of an image type, a processing purpose, and a way of use, because they have their own merits and demerits as stated above.
However, there has been provided no apparatus functioning as both the analog and the digital type color copying machines wherein the merits of both machines are realized. Hence, it has been necessary to use a very expensive digital copying machine for creating a highly fine color copy at excellent color reproduction.
Moreover, there has been provided no apparatus which allows an analog image and a digital image to be mixed on one copy.
For implementing the latter apparatus, the present applicant has proposed an image processing apparatus which is capable of outputting a high-resolution and high-color-reproduction image having an analog image and a digital image mixed thereon (U.S. patent application Ser. No. 07/624,729, filed on Dec. 11, 1990, U.S. Pat. No. 5,235,437).
The proposed image processing apparatus includes an analog writing system for analogously writing a reflected image data of an original onto a spatial light modulator employing a liquid-crystal when a light beam through the original from a light source is applied to the spatial light modulator, a digital reading system for digitally reading out an image data written on the spatial light modulator by two-dimensionally scanning the element with a laser beam, a processing unit for processing the read image data, a digital writing system for digitally writing the processed image data on the spatial light modulator by two-dimensionally scanning the element with a laser beam, and an analog reading system for analogously reading out the image data written on the spatial light modulator.
The scanning system for two-dimensionally moving the laser beam on the spatial light modulator for scanning the element will be described below.
The scanning system includes a laser beam source, lenses, a main-scanning galvanometer and a sub-scanning galvanometer.
The laser beam source, which can apply a laser beam to the spatial light modulator through the lenses so that the laser beam focuses on the spatial light modulator. On the optical path of the laser beam are provided the main-scanning galvanometer and the sub-scanning galvanometer, both of which serve to two-dimensionally move the focused laser beam on the spatial light modulator so that the laser beam spot is scanned on the modulator. That is, the main-scanning galvanometer serves to horizontally move the laser beam spot along one line and the sub-scanning galvanometer serves to vertically move the laser beam upper or lower to the next line. A scanning control unit is provided in the scanning system so as to supply a control signal for controlling the main-scanning and the sub-scanning galvanometers.
The scanning system further includes an F.theta. lens, a photo-detector and a lens. The F.theta. lens is used for correcting a difference between an optical length to the center of the spatial light modulator and the optical length to the peripheral portion of the element so that the laser beam is allowed to be focused at any location of the spatial light modulator.
The laser beam applied to the spatial light modulator is modulated therein and then applied to the photo-detector through the lens.
In the digital reading system, the laser beam source serves to apply the constant-intensity laser beam to the spatial light modulator through the main-scanning galvanometer and the sub-scanning galvanometer. Both galvanometers serve to two-dimensionally move the laser beam on the spatial light modulator so that the element is scanned with the laser beam. Then, the beam modulated in the spatial light modulator is received in the photo-detector.
In the digital writing system, a laser modulating circuit is provided so that the intensity of the laser beam emitted from the laser beam source is modulated. Then, the modulated laser beam is passed through the main-scanning galvanometer and the sub-scanning galvanometer so as to two-dimensionally scan the spatial light modulator.
The foregoing proposed image processing apparatus, however, requires a main-scanning mechanism and a sub-scanning mechanism for two-dimensionally moving a laser beam for scanning, that is, provides a more complicated optical system containing a scanning system. It results in lowering the productivity and reliability of the image processing apparatus and making the apparatus more bulky. In particular, in case that the digital reading and writing system are located in respective places, a pair of main-scanning and sub-scanning galvanometers are required for each system, resulting in making the apparatus more complicated.